Dihalopropyl ester antidotes for acetanilide herbicides

ABSTRACT

Antidote compounds for use with acetanilide herbicides having the formula ##STR1## in which X and X&#39; are halogens, independently selected from the group consisting of chlorine, bromine, and iodine; and 
     R is selected from the group consisting of alkyl having 1-12 carbon atoms, inclusive; halophenyl wherein halo is selected from the group consisting of chlorine, bromine and iodine; and substituted alkoxy carbonyl wherein the alkoxy group has 1-8 carbon atoms, inclusive and the substituents are halogen selected from the group consisting of chlorine, bromine and iodine; or dioxane.

FIELD OF THE INVENTION

This invention relates to antidotes for acetanilide herbicides and, more particularly, to dihalopropyl ester compounds which are useful as antidotes for acetanilide herbicides.

BACKGROUND OF THE INVENTION

An herbicide is a compound which controls or modifies plant growth, e.g., killing, retarding, defoliating, desiccating, regulating, stunting, tillering, stimulating, and dwarfing. The term "plant" refers to all physical parts of a plant, including seeds, seedlings, saplings, roots, tubers, stems, stalks, foliage, and fruits. "Plant growth" includes all phases of development from seed germination to natural or induced cessation of life.

Herbicides are generally used to control or eradicate weed pests. They have gained a high degree of commercial success because it has been shown that such control can increase crop yield and reduce harvesting costs.

The most popular methods of herbicide application include: pre-plant incorporation into the soil; in-furrow application to seeds and surrounding soil; pre-emergence surface treatment of seeded soil; and post-emergence treatment of the plant and soil.

A manufacturer of an herbicide generally recommends a range of application rates and concentrations calculated to maximize weed control. The range of rats varies from approximately 0.01 to 50 pounds per acre (0.0111 to 56 kilograms per hectare (k/ha)), and is usually in the range of from 0.1 to 25 pounds per acre (0.112 to 28 k/ha). The term "herbicidally effective amount" describes the amount of an herbicide compound which controls or modifies plant growth. The actual amount used depends upon several considerations, including particular weed susceptibility and overall cost limitations.

The most important factor influencing the usefulness of a given herbicide is its selectivity towards crops. In some cases, a beneficial crop is susceptible to the effects of the herbicide. In addition, certain herbicidal compounds are phytotoxic to some weed species but not to others. To be effective, an herbicide must cause minimal damage (preferably no damage) to the beneficial crop while maximizing damage to weed species which plague that crop.

To preserve the beneficial aspects of herbicide use and to minimize crop damage, many herbicide antidotes have been prepared. These antidotes reduce or eliminate damage to the crop without substantially impairing the damaging effect of the herbicide on weed species; See U.S. Pat. Nos. 4,021,224 and 4,021,229 and Belgian Pat. No. 846,894.

The precise mechanism by which an antidote reduces herbicidal crop injury has not been established. An antidote compound may be a remedy, interferent, protectant, or antagonist. As used herein, "antidote" describes a compound which has the effect of establishing herbicide selectivity, i.e., continued herbicidal phytotoxicity to weed species and reduced or non-phytotoxicity to cultivated crop species. The term "antidotally effective amount" describes the amount of an antidote compound which counteracts a phytotoxic response of a beneficial crop to an herbicide.

Acetanilide herbicides are particularly effective in the control of grassy type weeds which interfere with the cultivation of a wide variety of crops, e.g., barley, corn, cotton, lentils, peanuts, peas, potatoes, soybeans, spinach, tobacco and tomatoes. Frequently the effective use of these herbicides requires the addition of an antidote compound.

DESCRIPTION OF THE INVENTION

It has now been discovered that certain dihalopropyl ester compounds are effective antidotes for the protection of a variety of crops fromm acetanilide herbicide injuries. Such compounds have the following formula: ##STR2## in which X and X' are halogens, independently selected from the group consisting of chlorine, bromine, and iodine; and

R is selected from the group consisting of alkyl having 1-12 carbon atoms, inclusive; halophenyl wherein halo is selected from the group consisting of chlorine, bromine and iodine; and substituted alkoxy carbonyl wherein the alkoxy group has 1-8 carbon atoms, inclusive and the substituents are halogen selected from the group consisting of chlorine, bromine and iodine; or dioxane.

All carbon ranges are inclusive of both upper and lower limits. Exemplary of alkyl are methyl, ethyl, n-propyl, isopropyl and the like; exemplary of alkoxy are methoxy, ethoxy, and the like.

In a preferred embodiment, X and X' are both chlorine and R is selected from the group consisting of alkyl having 1-12 carbon atoms, inclusive; chloroethoxyethoxycarbonyl; chlorophenyl; (1-chloroethoxy-2-chloromethyl)ethoxy carbonyl; (1-chloroethoxyethoxy-2-chloromethyl)ethoxy carbonyl; and 1,4-dioxane methoxy carbonyl.

This invention embodies a two-part herbicidal system comprised of

(a) an herbicidally effective amount of an acetanilide compound of the formula ##STR3## in which R₁ and R₃ are independently selected from the group consisting of hydrogen; and alkyl having 1-6 carbon atoms, inclusive; and

R₂ is selected from the group consisting of alkyl having 1-6 carbon atoms, inclusive; alkoxyalkyl having 1-8 carbon atoms, inclusive; and carbethoxyalkyl wherein the alkyl group has 1-4 carbon atoms, inclusive; and

(b) a non-phytotoxic antidotally effective amount of a compound of the formula ##STR4## in which X and X' are halogens, independently selected from the group consisting of chlorine, bromine and iodine; and

R is selected from the group consisting of alkyl having 1-12 carbon atoms, inclusive; halophenyl wherein halo is selected from the group consisting of chlorine, bromine and iodine; and substituted alkoxy carbonyl wherein the alkoxy group has 1-8 carbon atoms, inclusive and the substituents are halogen selected from the group consisting of chlorine, bromine and iodine; or dioxane.

By way of exemplification, the active acetanilide herbicides employed in the invention may include the following: 2-chloro-2',6'-diethyl-N-(methoxymethyl)acetanilide; 2-chloro-2'-methyl-6'-ethyl-N-(methoxypropyl(2))acetanilide; 2-chloro-2',6'-dimethyl-N-(methoxyethyl)acetanilide; 2-chloro-2'-methyl-6'-ethyl-N-(ethoxymethyl)acetanilide; 2-chloro-N-isopropyl acetanilide; 2-chloro-2',6'-diethyl-N-(n-butoxymethyl)acetanilide; and 2-chloro-N-carbethoxymethyl-2',6'-diethyl acetanilide.

Preparation

The acetanilide herbicides of the present composition are either commercially available or can be prepared by the procedures described in U.S. Pat. Nos. 2,863,752; 3,442,945; 3,780,090; 3,937,730; 3,952,056; and 4,070,179.

The dihalopropyl ester antidote compounds of this invention can be prepared according to the following general procedure, depending upon the starting materials. 1,3-di-halo-2-propanol is reacted with an appropriate carbonyl chloride in a suitable solvent. Suitable solvent solutions include combinations of a basic component and a standard organic solvent. The basic component may be selected from the group consisting of a tertiary amine, an aromatic nitrogen, hydroxide, carbonate or bicarbonate. The standard organic solvent may be selected from the group consisting of hexane, dichloromethane, and other hydrocarbon, halocarbon, aromatic, ether and ketonic solvents. The preferred temperature range is between 0° and 40° C. After continuous stirring, the dihalopropyl ester may be extracted, dried, filtered and stripped. Structure may be confirmed by infrared (IR), nuclear magnetic resonance (NMR), or mass (MS) spectroscopy.

The following examples illustrate the preparation of specific compounds according to this general method. (Compound numbers correspond to those in Tables I, IV and V).

The following examples illustrate the preparation of specific compounds according to this general method. (Compound numbers correspond to those in Tables I, IV and V).

EXAMPLE 1 (Compound No. 1) Preparation of 1,3-Dichloroprop-2-yl acetate

Seventy-five grams (g) (0.581 mole) of 1,3-dichloro-2-propanol, 58.8 g (0.581 mole) of triethylamine, and 150 milliliters (ml) of hexane were combined in a reaction flask.

Forty-five and six-tenths grams (0.581 mole) of acetyl chloride were added to the reaction mixture through a drop funnel. During the period of acetyl chloride addition the reaction mixture was stirred constantly, the mixture was maintained under an argon atmosphere, and the temperature was maintained below 20° C. The mixture was stirred for 65 minutes.

The solution was filtered to remove hydrochloride. The hydrochloride was washed with hexane to remove excess 1,3-dichloroprop-2-yl acetate. The hexane extracts and the clear reaction solution were combined and washed with sodium carbonate, hydrochloric acid and water. The resulting solution was dried over magnesium sulfate, filtered, and stripped. The yield was 81.6 g 1,3-dichloroprop-2-yl acetate. Structure was confirmed by IR and NMR. (n_(D) ³⁰ =1.4531).

EXAMPLE 2 (Compound No. 6) Preparation of 1-(1,4-dioxanemethyl)-2-(1,3-dichloro-2-propyl)oxalate

One g (0.008 mole) of 1,3-dichloro-2-propanol, 0.9 g (0.009 mole) of triethylamine, and 50 ml of dichloromethane were combined in a reaction flask. Two and three tenths g (0.0088 mole) of 80% 1,4-dioxane-2-methyloxalyl chloride and 50 ml dichloromethane were added through a drop funnel. During the addition, the mixture was maintained under a nitrogen atmosphere, and the temperature was maintained below 20° C. The mixture was stirred overnight.

The mixture was washed with water, hydrochloric acid and sodium carbonate, dried over magnesium sulfate and stripped. The yield was 2.4 g 1-(1,4-dioxanemethyl)-2-(1,3-dichloro-2-propyl)oxalate. Structure was confirmed by MS and NMR. (n_(D) ³⁰ =1.4841).

The compounds prepared according to these procedures appear in Table I.

                                      TABLE I                                      __________________________________________________________________________     DIHALOPROP-2-YL ESTERS                                                          ##STR5##                                                                      Compound                                                                       No.   X X'                                                                               R                   Chemical Name      Physical                      __________________________________________________________________________                                                      Constant                      1     Cl                                                                               Cl                                                                               CH.sub.3            1,3-dichloroprop-2-yl acetate                                                                     n.sub.D.sup.30 = 1.4531       2     Cl                                                                               Cl                                                                                ##STR6##           (1,3-dichloroisopropyl)-2-(2-chloro-                                           ethoxyethyl) oxalate                                                                              n.sub.D.sup.30 = 1.4793       3     Cl                                                                               Cl                                                                                ##STR7##           1,3-dichloro-2-propyl-4-chlorobenzoate                                                            m.p. ≐ 82°      4     Cl                                                                               Cl                                                                                ##STR8##           1-[1-(2-chloroethoxy)-3-chloro-2- propyl]-2-                                   (1,3-dichloro-2-propyl) oxalate                                                                   n.sub.D.sup.30 = 1.4861       5     Cl                                                                               Cl                                                                                ##STR9##           1-(1-<2-(2-chloroethoxy)ethoxy>)-2-                                            (1,3-dichloro-2-propyl) oxalate                                                                   n.sub.D.sup.30 = 1.4841       6     Cl                                                                               Cl                                                                                ##STR10##          1-(1,4-dioxanemethyl)-2-(1,3- dichloro-2-pro                                   pyl) oxalate       n.sub.D.sup.30 = 1.4841       7     Cl                                                                               Cl                                                                               (CH.sub.2).sub.10 CH.sub.3                                                                         2,3-dichloro-2-propyl laurate                                                                     n.sub.D.sup.30 =              __________________________________________________________________________                                                      1.4566                   

Testing

Stock solutions of the herbicides were prepared by diluting the requisite amount of each herbicide in acetone. An example of a solution composition and application rate is summarized in Table II.

                  TABLE II                                                         ______________________________________                                         Herbicide Stock Solutions                                                                  Composition                                                                            Ace-                                                                   Herbicide                                                                              tone    Application                                        Herbicide Name                                                                               (mg)      (ml)    ml/flat*                                                                              lb/acre                                 ______________________________________                                         TERIDOX ® TECH                                                                           40        40      2      0.5                                     2-chloro-2',6'-                                                                dimethyl-N--(methoxy-                                                          ethyl) acetanilide                                                             ______________________________________                                          *The flats measure 5.95 inches by 9.5 inches. Approximately four (4)           mg/flat is equal to one (1) lb/acre.                                     

In each case, the herbicide was applied to the surface of the soil after planting of the seeds and prior to emergence of seedlings. In some cases the herbicide was applied to the soil alone after in-furrow application of the antidote; in others the herbicide solution was tank-mixed with the antidote solution prior to application.

Stock solutions of each antidote compound were prepared at the desired concentrations by diluting the requisite amounts of each antidote in acetone. Examples of solution compositions, rates and application methods are summarized in Table III.

                  TABLE III                                                        ______________________________________                                         Antidote Stock Solutions                                                       Antidote: Dihalopropyl esters                                                  Composition       Application                                                  Antidote (mg)                                                                             Acetone (ml)                                                                              ml/flat  lb/acre                                                                              Method                                    ______________________________________                                         100        15         1.5      5.00  IF*                                       100        15         3.0      5.00  PES**                                     ______________________________________                                          *IF = Infurrow surface application of antidote.                                **PES = Preemergent surface application of a tankmixed solution of             herbicide and antidote.                                                  

The antidote solutions were applied to the soil either by in-furrow surface application or by pre-emergent surface application. In all cases of pre-emergent surface application, the antidote was tank-mixed with the herbicide prior to application to the soil surface.

For in-furrow application, a one pint (473 cubic centimeter (cc)) sample of soil was removed and retained from each planting flat. After leveling and furrowing the soil, seeds of the crop or weed species were planted 1/2 inch deep (1.27 centimeter). Each flat was divided in half by a wooden barrier. A stock solution of the antidote was atomized directly onto the exposed seeds and soil in the open furrow on one side of the barrier. The seeds in the entire flat were then covered with the previously removed soil. The herbicide was applied to the surface of the soil in the flats after the seeds were covered over. The antidotally untreated sections of flats were compared for observed differences which would indicate lateral movement of the antidote through the soil.

Control flats contained crops treated with herbicide only.

All flats were placed on greenhouse benches where temperature was maintained between 70° and 90° F. (21.1° to 32.2° C.). The flats were watered by sprinkling as needed to assure good plant growth.

All of the soil used in the tests described herein was loamy sand soil treated with 50 parts per million (ppm) each of a commercially available fungicide, N-[(trichloromethyl)-thio]-4-cyclohexene-1,2-dicarboximide, and 18-18-18 fertilizer, which contains 18% by weight equivalent each of nitrogen, phosphorus pentoxide, and potassium oxide.

Injury ratings were taken four weeks after application of the antidote. The effectiveness of the antidote was determined by visual comparison of crop injury which occurred in the test flats to that which occurred in the control flats.

The crops screened for diminution of herbicidal injury were milo, wheat, barley, and corn. The weed species tested was watergrass (Echinochloa crusgalli).

KEY TO TABLES IV AND V

Compound numbers in these tables correspond to the numbers and their chemical description in Table I. Compounds omitted in Table V were not tested on weed species.

Herbicides

TERIDOX®--2-chloro-2',6'-dimethyl-N-(methoxyethyl)acetanilide

Application Methods

IF=In-furrow surface application of antidote (soil subsequently treated with herbicide only)

PES=Pre-emergent surface application of tank-mixed solution of herbicide and antidote.

If no antidote was applied, the word "none" appears in the Antidote Rate column. This is the control flat for each crop. The results shown on this line are the percent injuries sustained by each of the crops when treated with the herbicide only at the rate specified.

All rates shown, for both herbicide and antidote, are in pounds per acre.

Injury Ratings

The injury to the crop (Table IV) or weeds (Table V) is shown as a percentage of damage done to the plants as compared to an evaluation of the overall undamaged state of the plants. The damage done to the plants is a function of the number of plants injured and the extent of injury to each plant. This rating is made four (4) weeks after application of the herbicide alone or of the herbicide in combination with the antidote.

An asterisk (*) in Table IV indicates that the antidote compound is active in reducing herbicidal injury to the crop.

Table V shows that the antidote compounds tested have no effect on weeds, i.e., herbicidal injury to the weeds is sustained even in the presence of an antidote compound.

                                      TABLE IV                                     __________________________________________________________________________     Antidotal Effectiveness                                                        Cmpd.         Antidote  Milo                                                                               Wheat                                                                              Barley                                                                             Corn                                       No.  Herbicide                                                                            Rate                                                                              Rate Method                                                                              % Inj                                                                              % Inj                                                                              % Inj                                                                              % Inj                                      __________________________________________________________________________     Control                                                                             TERIDOX                                                                              0.5                                                                               none --    70 60   60  80                                        1    TERIDOX                                                                              0.5                                                                               5.00 IF   *50 60   60 *30                                             TERIDOX                                                                              0.5                                                                               5.00 PES   70 60   60 *45                                        2    TERIDOX                                                                              0.5                                                                               5.00 IF   *60 60  *50 *65                                             TERIDOX                                                                              0.5                                                                               5.00 PES  *50 60  *50 *70                                        3    TERIDOX                                                                              0.5                                                                               5.00 IF   *55 60  *45 *20                                             TERIDOX                                                                              0.5                                                                               5.00 PES  *55 60  *50 *50                                        4    TERIDOX                                                                              0.5                                                                               5.00 IF    70 60  *50 *40                                             TERIDOX                                                                              0.5                                                                               5.00 PES   70 60  *50  80                                        5    TERIDOX                                                                              0.5                                                                               5.00 IF    70 60   60  80                                             TERIDOX                                                                              0.5                                                                               5.00 PES  *60 60   60  80                                        6    TERIDOX                                                                              0.5                                                                               5.00 IF   *50 *30 *40 *15                                             TERIDOX                                                                              0.5                                                                               5.00 PES  *50 60  *50 *45                                        __________________________________________________________________________

                  TABLE V                                                          ______________________________________                                         Herbicidal Effectivenss                                                        Cmpd.                    Antidote                                              No.    Herbicide Rate    Rate   Method Watergrass                              ______________________________________                                         Control                                                                               TERIDOX   0.5     none   --     100                                     1      TERIDOX   0.5     5.00   IF     100                                            TERIDOX   0.5     5.00   PES    100                                     2      TERIDOX   0.5     5.00   IF     100                                            TERIDOX   0.5     5.00   PES    100                                     3      TERIDOX   0.5     5.00   IF     100                                            TERIDOX   0.5     5.00   PES    100                                     4      TERIDOX   0.5     5.00   IF     100                                            TERIDOX   0.5     5.00   PES    100                                     5      TERIDOX   0.5     5.00   IF     100                                            TERIDOX   0.5     5.00   PES    100                                     6      TERIDOX   0.5     5.00   IF     100                                            TERIDOX   0.5     5.00   PES    100                                     ______________________________________                                    

Test Results

The compounds of this invention show good antidotal activity for a variety of crops. The composition of acetanilide herbicide and antidote compound was particularly effective for the reduction of herbicidal injury to corn crops. Use of the antidote compounds did not result in a reduction of herbicidal injury to weeds.

Formulations

A formulation is the incorporation of a formulant in a form which is directly usable on crops and weeds. As defined herein, a "formulant" is the material which is to be formulated. The formulant may be either an antidote compound alone or an herbicide and antidote composition. The purpose of the formulation is to apply the formulant to the locus where it is desired to establish herbicidal selectivity by a convenient method. The "locus" may include soil, seeds, seedlings and vegetation.

The formulations are commonly dusts, wettable powders, granules, solutions or emulsifiable concentrates.

Dusts are free-flowing powder compositions containing the formulant impregnated on a particulate carrier. The particle size of the carriers is usually in the approximate range of 30 to 50 microns. Examples of suitable carriers are talc, bentonite, diatomaceous earth, and pyrophyllite. The composition generally contains up to 50% of formulant. Anti-caking and anti-static agents may also be added. Dusts may be applied by spraying from boom and hand sprayers on airplanes.

Wettable powders are finely divided compositions comprising a particulate carrier impregnated with the formulant and additionally containing one or more surface active agents. The surface active agent promotes rapid dispersion of the powder in an aqueous medium to form stable, sprayable suspensions. A wide variety of surface active agents can be used, for example, long chain fatty alcohols and alkali metal salts of the sulfated fatty alcohols; salts of sulfonic acid; esters of long chain fatty acids; and polyhydric alcohols, in which the alcohol groups are free, omegasubstituted polyethylene glycols of relatively long chain length. A list of surface active agents suitable for use in agriculture formulations can be found in Wade Van Valkenburg, Pesticide Formulations (Marcel Dekker, Inc., N.Y., 1973) at pages 79-84.

Granules comprise the formulant impregnated on a particulate inert carrier having a particle size of about 1 to 2 millimeters (mm) in diameter. The granules can be made by spraying a solution of the formulant in a volatile solvent onto the granular carrier. Examples of suitable carriers for the preparation of granules include clay, vermiculite, sawdust, and granular carbon.

Emulsifiable concentrates consist of an oil solution of the formulant plus an emulsifying agent. Prior to use the concentrate is diluted with water to form a suspended emulsion of oil droplets. The emulsifiers used are usually a mixture of anionic and nonionic surfactants. Other additives, such as suspending agents and thickeners, may be included in the emulsifiable concentrate.

When the formulant is an antidote and herbicide composition, the proportion of antidote compound to herbicide compound generally ranges from approximately 0.001 to 30 parts by weight of the antidote compound per weight of the herbicide compound.

Formulations generally contain several additives in addition to the formulant and carrier or agent. Among these are inert ingredients, diluent carriers, organic solvents, water, oil and water, water in oil emulsions, carriers of dusts and granules, and surface active wetting, dispersing and emulsifying agents. Fertilizers, e.g., ammonium nitrate, urea and superphosphate, may be included. Aids to rooting and growth, e.g., compost, manure, humus and sand, may also be included.

As another alternative, the formulant can be applied to the soil in the form of a solution in a suitable solvent. Solvents frequently used in these formulations include kerosene, fuel oil, xylene, petroleum fractions with boiling ranges above xylene and aromatic petroleum fractions rich in methylated naphthalenes. Liquid solutions, like dusts, may be applied by spraying from boom and hand sprayers on airplanes. 

What is claimed is:
 1. A composition comprising:(a) an herbicidally effective amount of an acetanilide compound of the formula ##STR11## in which R₁ and R₃ are independently each alkyl having 1-2 carbon atoms, inclusive; andR₂ is alkoxyalkyl having 1-4 carbon atoms, inclusive; and (b) a non-phytotoxic antidotally effective amount of a compound of the formula ##STR12## in which X and X' are halogens, independently selected from the group consisting of chlorine, bromine and iodine; andR is dioxane-substituted alkoxy carbonyl wherein the alkoxy group has 1-4 carbon atoms, inclusive.
 2. A composition according to claim 1 in which X and X' are both chlorine.
 3. A composition according to claim 2 wherein R is 1,4-dioxanemethoxy carbonyl.
 4. A composition according to claim 1 wherein R₁ and R₃ are both methyl and R₂ is methoxyethyl.
 5. A method of controlling undesirable vegetation and reducing herbicidal crop injury due to an acetanilide herbicide which comprises applying to the locus where control is desired an herbicidally effective amount of a composition comprising:(a) an herbicidally effective amount of an acetanilide compound of the formula ##STR13## in which R₁ and R₃ are independently each alkyl having 1-2 carbon atoms, inclusive; andR₂ is alkoxyalkyl having 1-4 carbon atoms, inclusive; and (b) a non-phytotoxic antidotally effective amount of a compound of the formula ##STR14## in which X and X' are halogens, independently selected from the group consisting of chlorine, bromine and iodine; andR is dioxane-substituted alkoxy carbonyl wherein the alkoxy group has 1-4 carbon atoms, inclusive;wherein the antidote is applied to the seeds and soil prior to the application of the acetanilide herbicide to the pre-emergence soil surface.
 6. A method according to claim 5 in which X and X' are both chlorine.
 7. A method according to claim 6 wherein R is 1-4-dioxanemethoxy carbonyl.
 8. A method according to claim 5 wherein R₁ and R₃ are both methyl and R₂ is methoxyethyl.
 9. A formulation comprising an herbicidally effective amount of 2-chloro-2',6'-dimethyl-N-(methoxyethyl)acetanilide and an antidotally effective amount of 1-(1,4-dioxanemethyl)-2-(1,3-dichloro-2-propyl)oxalate. 